In the proposed program, sensors based on electrochemical principles would be developed using chemically modified electrode technology. The development of amperometric, immobilized enzyme electrodes with electron transfer from the enzyme mediated by a polymer-immobilized redox couple on a metallic electrode is recommended. Selectivity will be afforded by use of glucose oxidase as the primary reactant with glucose. The reliability of the sensor will be subject to optimization by the selection of redox couples to provide fast regeneration of the reduced form of glucose oxidase, and by selection of immobilization techniques and membranes which exclude large biological molecules. Sensors of the type envisioned here can be made quite small, and would require a minimum of low-power electronics for operation. Initial work at SumX has demonstrated the use of an electroactive polymer modified metal electrode to mediate the oxidation of glucose by glucose oxidase. The objectives of the Phase I project will be to determine if truly rugged sensors of this type can be constructed using polymer-immobilized redox couples on metallic electrodes and operated for extended times in physiological media.